The heart pumps blood throughout the extremities to provide essential oxygen and nutrients to the tissue in the extremities. The deoxygenated and waste product laden blood is then returned to the heart and internal organs for cleansing and oxygenation, and then is repumped to the body.
The return flow occurs, in part, due to the pressure generated in the veins, the pull of the right auricle of the heart, and through the milking effect of the muscle contractions in the extremities, particularly the “calf pump” mechanism of the lower extremities.
Muscle contractions that occur during activities of daily living facilitate this return flow of blood, but prolonged sitting or standing causes deoxygenated blood to stagnate. This leads to general fatigue and tired, heavy legs, and edema. Over a period of time, repetition of this cycle can lead to more serious conditions such as varicose veins, Restless Leg Syndrome, neuropathies, deep vein thrombosis, and leg ulcerations, to name a few.
In order to facilitate return blood flow a number of expedients have been employed. For those who are bedridden, intermittent external compression is used, primarily designed to prevent deep vein thrombosis. External compressive hose are often worn by those with leg circulatory issues.
Other devices have been proposed for physical therapy or exercise that utilize a foot pedal or treadle type arrangement, which allows a person a controlled exercise regimen using their feet and ankles to manipulate against a resistance foot pedal. For example in Kane et al., U.S. Pat. No. 4,501,421, a foot treadle device operates to provide a resistance force to the pivoting of foot plates. Shimizu, U.S. Pat. No. 3,741,540, discloses foot boards mounted for pivoting with springs providing resistance. A similar device is seen in Kuo, U.S. Pat. No. 6,705,975. It is has also been recognized that even passive motion, where no muscle activity from the user is required, may provide benefits. Matthew, U.S. Pat. No. 6,758,825, provides a foot pedal, with straps to secure the user's foot on the device, which is attached to a reciprocating motor. The motor rotates forcing a reciprocating rod in a circular motion, which is translated into an approximate linear motion for the foot pedal. This causes a back-and-forth motion for the foot. While the Matthew device is anticipated to have use in a variety of contexts, it is primarily designed for people who may have severe physical impairments, such as those confined to a wheelchair. The motor assisted motion prevents deterioration in muscles, which would otherwise be flaccid or unexercised because of some physical or nerve condition that prevents the patient from exercising those muscles themselves. The Matthew device facilitates blood flow in the veins and, therefore, may prevent deep venous thrombosis. Despite this earlier work, there is still an unmet need for a physical exercise device which is simple to construct, inexpensive to produce, can be widely distributed, be used in a wide variety of clinical, home, and office settings to produce high repetitions, without muscle fatigue, to purge the circulatory system of the legs.